you mean this entire time you weren't running the fans at 100%? these sapph cards are just really bad for VRM cooling, run them at 100% and have your mind at a bit more ease. Yes the noise will be louder but you're already running a 50 card farm....

also it seems that alot people using splitters on PSU are burning out high powered 280/290 cards. am running over 40 R9 290 from XFX for over 2 months with 0 issues all cards are running 830/850 kh/s , 3 cards per system using a proper PSU corsair AX1200, each system load is 960 watts.